$1,099,000
507 Monte Diablo Ave, San Mateo 94401
AddressIntel AI Briefing
The optimal play is stealth density: primary + ADU + JADU to maximize the site without triggering a full teardown. While the 119-year-old structure is a natural teardown candidate, a full new build is severely hindered by a liquefaction hazard zone and low median household income in the immediate census tract. Retaining the existing footprint avoids costly geotechnical foundation upgrades required for new construction.
Property Permit History
Recent Neighborhood Remodeling (San Mateo)
Parcel & Zoning Info
ADU Potential
Flag / irregular · Corner lot · ~98 ft frontage × 106 ft deep, a tucked-away rear unit is very private; access is typically via the pole driveway. A second street frontage lets an ADU take its own entrance and address.
Screening heuristic based on lot size, existing coverage, lot orientation, and hazard overlays. CA ADU law is ministerial statewide; verify max size, setbacks, and JADU owner-occupancy with the local planning dept.
Redevelopment Potential
Meaningful unused floor-area headroom under current zoning, room to add square footage. Zoning allows roughly 2,100 sqft of gross floor area on this lot.
Screening estimate comparing existing living area to the city's single-family floor-area limit. FAR figure is a discretionary-review trigger, not a hard cap. Treat as approximate. Source: San Mateo Muni Code 27.18.060 (R1-B/C); 6,000 sqft cap (as of 2026-06-30). Verify FAR, coverage, setbacks, and height with the local planning dept.
Hazard Snapshot
Flood Zone
Fire Severity
Liquefaction
Fault Zone
Not a substitute for a Natural Hazard Disclosure (NHD) report. Zones reflect available GIS data and may not cover all localities.
Nearby Public Schools
College Park Elementary
San Mateo-Foster City
Borel Middle
San Mateo-Foster City
San Mateo High
San Mateo Union High
School boundaries are subject to change. Nearest school distance does not guarantee enrollment eligibility. Check with the local district. Data provided by CDE.
Proprietary Intelligence
Market Heat Index
67/100
Based on recent sales velocity and local demand in 94401.
Flippability Score
65/100
Measures neighborhood renovation density vs. recent permits on this property.
Bidding War Prob.
47%
Likelihood of multiple offers based on local list-to-sale ratios and DOM.
Proforma ROI Calculator
Back-of-the-napkin deal analysis across development strategies.
Zoning allows roughly 2,100 sqft on this lot, and the default builds to that envelope. The FAR figure is a discretionary-review trigger, not a hard cap.
Median of 12 recent single-family sales in San Mateo (94401): $860/sqft. Sized within 25% of the 2,100 sqft build, because smaller houses sell for more per foot and pricing a rebuild off them overstates resale.
Commission, transfer tax and closing. Deducted from resale before profit, so the ROI below is net of the exit rather than gross.
Carry on total capital for the project duration. At 0% the model is a cash purchase; 12 months at a typical construction-loan rate moves ROI by 6 to 10 points on a deal this size, so price it with your real rate.
Projected Profit
Warning: Project is mathematically underwater.
Recent Comparables (San Mateo 94401)
Sized to the modelled 2,100 sqft build: sales within 25% of it. Smaller houses sell for more per foot, so pricing a rebuild off them overstates resale.